<wicket:extend xmlns:wicket="http://wicket.apache.org">

    <a wicket:id="expandAll" class="button-link">Expand all nodes</a>&#160;&#160;
    <a wicket:id="collapseAll" class="button-link">Collapse all nodes</a>&#160;&#160;
    <a wicket:id="switchRootless" class="button-link">Switch rootless mode</a>
    <br>
    <wicket:child/>
    
</wicket:extend>